The problem I have with this pertains to the Observer Effect as well as the proposed Multiverse of timelines/potentialities.
As such, nothing/no event observed can be destroyed, changed, or undone.
This protects causality and prevents paradox.
1. Time Traveller A goes back in time, and prevents the assassination of JFK.
2. The Assassination of JFK remains a historical reality in Time Traveller A's point of origin.
3. The prevention of the Assassination of JFK by Time Traveller A creates a new timeline/universe where JFK was never assassinated.
4. Other time travellers from the same point of origin as Time Traveller A can still visit the observed Assassination as it happened originally, or
choose to visit the new affected version/timeline/universe caused by Time Traveller A.
As such, there's no cause or reason for any Time Police.
All observed events are already observed and thus indestructible from point of perspective of point of origin.
Tangent to this, any Time Traveller could then create as many universes/versions/timelines as they desired with as many different outcomes for any and
every event since the beginning of Time, until the end of Time without ever breaking causality, causing paradox, altering their true point of origin,
or anything else observed.
This additionally allows for the existence of Time Travel as a reality, effectively making the argument that Time Travel can not exist obsolete.
Welcome to the multiverse.
edit on 11/9/2013 by AliceBleachWhite because: (no reason given)